VINSOL.RTM. (commercially available from Hercules, Inc.) is a high-molecular weight product consisting primarily of a phenolic fraction (57%), a hydrocarbon fraction (15%), and a rosin-based fraction (28%). Each fraction is a combination of a variety of chemical substances. Emulsion formulators commonly use VINSOL as an anionic emulsifier in order to achieve desired mixing stabilities and drying characteristics for slow-setting asphalt emulsions. However, as VINSOL is obtained from tree stumps as a residue of wood rosin manufacturing processes, there exists some question as to whether the increasing commercial demand for this product will be met in the future.
Emulsions prepared with the sodium or potassium soap of VINSOL are, in most cases, of the slow-set type. That is, the emulsions are stable enough when mixed with Portland cement to conform with the specifications of A.S.T.M. D244 defining a slow-setting emulsion (which allows a maximum of one percent of coagulated emulsion to be retained on a No. 14 sieve). The results of the cement mixing test can vary with the amount of the emulsifier used, the pH of the soap solution, and the type of asphalt employed.
Tall oil fatty acids, tall oil rosins, gum and wood rosin, and other fatty carboxylic acids isolated from vegetable or animal oils or fats are common emulsifiers for anionic asphalt emulsions. However, the combination of fatty polycarboxylic acid emulsifiers with Portland cement invariably produces rapid-setting emulsions with minimum mixing stabilities. Likewise, when fatty polycarboxylic acid-based emulsion mixes are used with dense-graded fine aggregates or clay, the electrostatic charges between the aggregate particles cause the emulsions to break immediately upon contact. This renders such emulsions inadequate for slurry seal applications and thixotropic industrial emulsion applications which contain clay and/or polymer latex.
The use of high acidity asphalts also generally results in the formation of rapid or medium-setting emulsions having high cement mix residues. Formulators have traditionally used blends of VINSOL and INDULIN.RTM. C (a kraft lignin sodium salt commercially available from Westvaco, Inc.) with high acidity asphalts in order to obtain emulsions with slow-set characteristics.
In commonly assigned U.S. Pat. No. 4,676,927, Schilling et al. teach the production of rapid-setting and medium-setting aqueous bituminous emulsions. The patent teaches the employment of an anionic emulsifier at levels of between 0.4 to 0.6% for rapid-setting applications and between 0.6 to 3.0% for medium-setting applications. However, emulsions taught by the patent are to be unsuitable for use as storage-stable, slow-setting aqueous anionic bituminous emulsions, especially in applications where fine aggregates or clay is required.
Therefore, it is an object of this invention to produce an alternative to VINSOL for use in formulating anionic bituminous emulsions.
Another object of this invention is to formulate stable slow-setting anionic bituminous emulsions suitable for use with fine aggregates in slurry seal applications.
A further object of this invention is to formulate stable slow-setting anionic bituminous emulsions suitable for use with clays and/or polymer latices in industrial emulsion applications.